Combination HIV prevention demonstrates significant promise in reducing burden of disease. To maximize its effectiveness combination prevention must be tailored to a given context and population. From the beginning of the global HIV epidemic, female sex workers (FSWs) have been found to be at heightened risk for infection. More recently the role that sex work plays in ongoing HIV transmission dynamics has been more clearly established in generalized epidemics, where previously limited attention was paid to the role of key populations. The greater vulnerability of FSWs is now widely understood to be associated with social and structural factors including the intense stigma, discrimination and violence they often face and the unsafe environments in which they live and work. These factors are known to limit both protective sexual behaviors and engagement in HIV testing, care and treatment services. Comprehensive, community-based HIV prevention approaches addressing the aforementioned social and structural vulnerabilities to HIV infection among FSWs have been shown to be effective in South Asia and in Latin America. However, in sub-Saharan Africa where the impact of HIV is the greatest, no systematic efforts to develop and evaluate the feasibility and effectiveness of community-based combination HIV prevention among FSWs has occurred. We propose to conduct a two-arm Phase II community randomized controlled trial of a community-based combination HIV prevention intervention among FSWs in Iringa, Tanzania. The model was developed on the basis of prior formative research and mapping and utilizes an ongoing research infrastructure. The combination package will include integrated biomedical, behavioral and structural components: (1) mobile HIV testing and risk reduction counseling; (2) service navigation to facilitate access to treatment and retention in care; (3) sensitivity trainin for HIV clinical care providers; (4) SMS text messages to promote adherence to care and ART; (5) venue-based peer education and condom distribution; and (6) a community drop- in-center to promote cohesion and collective action to reduce stigma and discrimination. We seek to establish base rates of key outcomes including HIV incidence and viral load suppression, examine the socio-structural and behavioral pathways of the intervention, assess feasibility, acceptability and safety, and document preliminary effectiveness. Should compelling indications of safety, feasibility, acceptability and initial effectiveness be found, study results will informthe first Phase III RCT of community-based combination HIV prevention among FSWs.